Novel superhard dielectric compounds useful as gate dielectrics discovered. Low temperature methods for making thin films of the compounds on substrate silicon are provided. The methods comprise the step of contacting a precursor having the formula H.sub.3X--O--XH.sub.3, wherein X is silicon or carbon with a compound comprising boron or nitrogen in a chemical vapor deposition (CVD) chamber or with one or more atomic elements in a molecular beam epitaxial deposition (MBE) chamber. These thin film constructs are useful as components of microelectronic devices, and specifically as gate dielectrics in CMOS devices.